8
3. The following types of installation may require Outdoor
Air for combustion, due to chemical exposures:
• Commercial buildings
• Buildings with indoor pools
• Furnaces installed in laundry rooms
• Furnaces installed in hobby or craft rooms
• Furnaces installed near chemical storage areas
Exposure to the following substances in the combus-
tion air supply may also require Outdoor Air for
combustion:
• Permanent wave solutions
• Chlorinated waxes and cleaners
• Chlorine based swimming pool chemicals
• Water softening chemicals
• De-icing salts or chemicals
• Carbon tetrachloride
• Halogen type refrigerants
• Cleaning solvents (such as perchloroethylene)
• Printing inks, paint removers, varnishes, etc.
• Hydrochloric acid
• Cements and glues
• Antistatic fabric softeners for clothes dryers
• Masonry acid washing materials
!
WARNING:
Furnace installation using methods other than
those described in the following sections must
comply with the National Fuel Gas Code and all
applicable local codes to provide sufficient
combustion air for the furnace.
Installation In An Unconfined Space
An unconfined space is an area including all rooms not
separated by doors with a volume greater than 50 cubic feet
per 1,000 Btuh of the combined input rates of all appliances
which draw combustion air from that space.
For example, a space including a water heater rated at
45,000 Btuh input and a furnace rated at 75,000 Btuh
requires a volume of 6,000 cubic feet [50 x (45 + 75) =
6,000] to be considered unconfined. If the space has an 8
foot ceiling, the floor area of the space must be 750 square
feet (6,000 / 8 = 750). In general, a furnace installed in an
unconfined space will not require outside air for combustion.
However, in “tight” buildings (with weather stripping and
caulk to reduce infiltration), it may be necessary to provide
outside air to ensure adequate combustion and venting,
even though the furnace is located in an unconfined space.
Installation In A Confined Space
A confined space is an area with volume less than 50 cubic
feet per 1,000 Btuh of the combined input rates of all
!
WARNING:
Do not place combustible material on or against
the furnace cabinet or within 6 inches of the vent
pipe. Do not place combustible materials,
including gasoline and any other flammable
vapors and liquids, in the vicinity of the furnace.
VENTING AND COMBUSTION
AIR REQUIREMENTS
General
Provisions must be made in the installation of this furnace
to provide an adequate supply of air for combustion. Detailed
instructions for determining the adequacy of an installation
can be found in the current revision of the National Fuel Gas
Code (ANSI Z223.1 / NFPA54) or in applicable local building
codes. Consult local codes for special requirements.
For Canadian installations consult Canadian Installations
Codes and (CAN/CGA B149.1 or .2).If the furnace is
operated with inadequate air for combustion
one of the flame roll-out switches located in the burner
compartment or the vent switch will open, turning off the
gas supply to the burners. These safety devices are
manually reset switches. DO NOT install jumper wires
across these switches to defeat their function. DO NOT
reset a switch without identifying and correcting the fault
condition. If a switch must be replaced, use only the
correct part specified in the Replacement Parts List.
Air openings in the furnace door, warm air registers, and
return air grilles must not be restricted.
!
CAUTION:
Combustion air must not be drawn from a
corrosive atmosphere.
To maximize heat exchanger life, the combustion air must
be free of chemicals which form corrosive acidic compounds
in the combustion gases.
Combustion Air Quality
The recommended source of combustion air is to use the
outdoor air supply. However, the use of indoor air in most
applications is acceptable except as follows:
1. If the furnace is installed in a confined space it is
recommended that the necessary combustion air come
from the outdoors by way of attic, crawl space, air duct,
or direct opening.
2. If outdoor combustion air is used, there must be no
exposure to the installations or substances listed in
Item 3 below.
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